Update dependency to fix goroutine proliferation in zipkin-go

[mandarjog]

This PR fixes goroutine proliferation issue with openzipkin-go. https://github.com/istio/issues/issues/100#issuecomment-339468537

After the PR is upstreamed, we will update the dependency.

https://github.com/mandarjog/zipkin-go-opentracing/pull/1

Release note:

NONE

---

This change is 

[jmuk]

collected some data points for this PR -- in short, this seems solving the reported problem (istio/issues#100).

My setup is to simply deploy the istio-auth (without zipkin pod), bookinfo sample, and run wrk to the productpage for 5 minutes.

The red line in the following graph shows the heap alloc bytes data (tracked by prometheus), with this PR (green is proxy -- unrelated, same in the following graphs):

Without this PR, typically heap allocation looks like

note that the spiky pattern happens after wrk run finishes -- still using memory for zipkin, we guess.

The number of goroutines,

Still have some increases since gRPC creates a goroutine for every request, but actually, the goroutine count looks like as follows without this PR

and note that, with the scale of the latter graph, the former goroutine "increase" looks like a flat line.

[jmuk]

/lgtm

[douglas-reid]

/lgtm

[douglas-reid]

/approve

[istio-merge-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: douglas-reid, jmuk

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these OWNERS Files: - ~~[OWNERS](https://github.com/istio/mixer/blob/master/OWNERS)~~ [douglas-reid] You can indicate your approval by writing `/approve` in a comment You can cancel your approval by writing `/approve cancel` in a comment

[istio-merge-robot]

/test all [submit-queue is verifying that this PR is safe to merge]

[istio-merge-robot]

Automatic merge from submit-queue.

[codecov[bot]]

Codecov Report

Merging #1515 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1515   +/-   ##
=======================================
  Coverage   84.58%   84.58%           
=======================================
  Files         122      122           
  Lines       11999    11999           
=======================================
  Hits        10149    10149           
  Misses       1648     1648           
  Partials      202      202

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update bbd5e27...6e2fca0. Read the comment docs.